1. Field of the Invention
The present invention relates to a method for finishing a metal line for a semiconductor device, and more particularly, to a method for finishing a metal line for a semiconductor device in which a chlorine radical and a chlorine compound generated when forming a metal line for a semiconductor device including aluminum and its alloy are removed using H2O plasma to prevent the metal line from being eroded and a polymer generated when forming the metal line is effectively removed using H2O gas and HF gas to improve reliability and yield of the semiconductor device.
2. Discussion of the Related Art
Recently, with rapid development of information media such as computers, the manufacture technology of a semiconductor device has been developed rapidly. The technology of the semiconductor device is being developed in such a way that its integration, miniaturization, and operational speed are improved.
Aluminum or its alloy having excellent electric conductivity and low cost is widely used as a material of a metal line for a high integrated circuit such as a very large-scale integrated (VLSI) circuit.
Generally, the process of forming a metal line of aluminum includes the steps of forming an aluminum film, coating a photoresist on the aluminum film and patterning it, etching the aluminum film exposed without being covered with the photoresist using plasma including a chlorine radical, and stripping the photoresist.
FIG. 1A to FIG. 1C are sectional views illustrating a related art method for finishing a metal line for a semiconductor device.
First, as shown in FIG. 1A, a photoresist 110 is coated on a substrate 100 on which an oxide film 102, a barrier film 104, an aluminum film 106 and an antireflective coating film 108 are sequentially formed. The photoresist 110 is then patterned so that the aluminum film 106 is dry-etched by plasma including chlorine using the patterned photoresist 110 as a mask. At this time, chlorine is reacted with the aluminum film 106 and the photoresist 110 to form a polymer 112 containing chlorine. The polymer 112 is coated on a surface of the aluminum film 105.
Next, as shown in FIG. 1B, a strip process is performed to remove the photoresist 110. When the photoresist 110 is removed, the polymer 112 is partially removed but still remains on the surface of the aluminum film 106. If the polymer 112 is exposed to the air, H2O in the air is reacted with chlorine to form hydrogen chloride (HCl). The hydrogen chloride erodes the aluminum film 106 to degrade electrical characteristics of the semiconductor device or cause a defect such as short in a serious case. The remaining polymer causes a defect in a later process to reduce yield of the semiconductor device.
As methods for finishing the metal line to remove erosion and polymer, there are provided a method for washing the metal line using deionized water, a method for evaporating the metal line using an annealing process, and a method for finishing the metal line using plasma containing fluorine (F).
However, the method for washing the metal line using deionized water has drawbacks in that it fails to perfectly remove the polymer and prevent the aluminum line from being eroded for the long run. The method for evaporating the metal line using an annealing process has drawbacks in that it causes hillock, segregation, and recrystallization if an annealing temperature exceeds 300° C. due to a low melting point of aluminum.
The method for finishing the metal line using plasma containing fluorine, as disclosed in the Korean Laid-Open Patent No. 2000-0027241, is to remove polymer and photoresist remaining after etching polymer using an etching gas containing fluorine, using an ashing process. However, as shown in FIG. 1C, such a finishing process has problems in that undercut 114 of a barrier film of TiN or TiW is caused by fluorine plasma, excessive loss of a lower oxide film is caused, and aluminum is transformed into AlF3 to remarkably reduce reliability of the semiconductor device.
In a more improved process for manufacturing a semiconductor device, to prevent chlorine and H2O exposed to the air from being reacted with each other, an etching equipment is provided with an ashing chamber to perform a strip process of photoresist in-situ. Hydrogen chloride is formed using H2O plasma before polymer is removed using plasma containing fluorine and then exhausted by pumping to remove polymer or a chlorine radical remaining on the surface of aluminum. However, since plasma containing fluorine is used, there still exist the aforementioned problems.